chemistry 11 sch3u test 4 – solutions and solubility
name:_____________________________

multiple choise questions: k/u-10

1. which of the following is the correct dissociation reaction for calcium hydroxide?
a. $\ce{ca(oh)_{2(s)} \
ightarrow ca^{2+}_{(aq)} + 2oh^{-}_{(aq)}}$
b. $\ce{caoh_{(s)} \
ightarrow ca^{+}_{(aq)} + oh^{-}_{(aq)}}$
c. $\ce{ca(oh)_{2(s)} \
ightarrow 2ca^{2+}_{(aq)} + oh^{-}_{(aq)}}$
d. $\ce{ca(oh)_{3(s)} \
ightarrow ca^{3+}_{(aq)} + 3oh^{-}_{(aq)}}$

2. the ph scale measures
a. the level of saltiness of a solution
b. concentration of $\ce{oh^{-}_{(aq)}}$ ions
c. concentration of acids
d. concentration of $\ce{h^{+}_{(aq)}}$ ions
e. none of the above

3. which of the following best describes a weak acid?
a. an acid that is not very strong
b. a dilute strong acid
c. an acid with a very low concentration
d. an acid that dissociates very slightly in a water solution
e. an acid that ionizes very slightly in a water solution

4. if a ph meter was placed in a 1.4 mol/l solution of nitric acid the reading would be which of the following?
a. 1.4
b. 14.15
c. $-0.15$
d. 0.15
e. 0.0

5. a solution that contains the maximum quantity of a solute at a specific temperature is
a. saturated
b. unsaturated
c. supersaturated
d. dissolved
e. none of the above

6. which of the following is not a property of acids?
a. they taste sour
b. they have a ph less than 7.
c. they react with metals.
d. they do not react with carbonates.
e. they turn blue litmus red.

Question

chemistry 11 sch3u test 4 – solutions and solubility
name:_____________________________

multiple choise questions: k/u-10

1. which of the following is the correct dissociation reaction for calcium hydroxide?
   a. $\ce{ca(oh)_{2(s)} \
ightarrow ca^{2+}_{(aq)} + 2oh^{-}_{(aq)}}$
   b. $\ce{caoh_{(s)} \
ightarrow ca^{+}_{(aq)} + oh^{-}_{(aq)}}$
   c. $\ce{ca(oh)_{2(s)} \
ightarrow 2ca^{2+}_{(aq)} + oh^{-}_{(aq)}}$
   d. $\ce{ca(oh)_{3(s)} \
ightarrow ca^{3+}_{(aq)} + 3oh^{-}_{(aq)}}$

2. the ph scale measures
   a. the level of saltiness of a solution
   b. concentration of $\ce{oh^{-}_{(aq)}}$ ions
   c. concentration of acids
   d. concentration of $\ce{h^{+}_{(aq)}}$ ions
   e. none of the above

3. which of the following best describes a weak acid?
   a. an acid that is not very strong
   b. a dilute strong acid
   c. an acid with a very low concentration
   d. an acid that dissociates very slightly in a water solution
   e. an acid that ionizes very slightly in a water solution

4. if a ph meter was placed in a 1.4 mol/l solution of nitric acid the reading would be which of the following?
   a. 1.4
   b. 14.15
   c. $-0.15$
   d. 0.15
   e. 0.0

5. a solution that contains the maximum quantity of a solute at a specific temperature is
   a. saturated
   b. unsaturated
   c. supersaturated
   d. dissolved
   e. none of the above

6. which of the following is not a property of acids?
   a. they taste sour
   b. they have a ph less than 7.
   c. they react with metals.
   d. they do not react with carbonates.
   e. they turn blue litmus red.

Accepted Answer

### Question 1
# Brief Explanations:
Calcium hydroxide has the formula $ \text{Ca(OH)}_2 $. When it dissociates, it should produce one $ \text{Ca}^{2+} $ ion and two $ \text{OH}^- $ ions. Option a shows $ \text{Ca(OH)}_{2(\text{s})}
ightarrow \text{Ca}^{2+}_{(\text{aq})} + 2\text{OH}^-_{(\text{aq})} $, which is correct. Option b has the wrong formula for calcium hydroxide (should be $ \text{Ca(OH)}_2 $, not $ \text{CaOH} $) and wrong charge on Ca. Option c has incorrect stoichiometry (2 $ \text{Ca}^{2+} $ instead of 1). Option d has the wrong formula (should be $ \text{Ca(OH)}_2 $, not $ \text{Ca(OH)}_3 $) and wrong charge on Ca.
# Answer:
a. $ \text{Ca(OH)}_{2(\text{s})}
ightarrow \text{Ca}^{2+}_{(\text{aq})} + 2\text{OH}^-_{(\text{aq})} $

### Question 2
# Brief Explanations:
The pH scale is defined as $ \text{pH} = -\log[\text{H}^+] $, so it measures the concentration of $ \text{H}^+_{(\text{aq})} $ ions. Option a is incorrect (saltiness is related to salt concentration, not pH). Option b is incorrect (pOH measures $ \text{OH}^- $ concentration). Option c is incorrect (pH measures $ \text{H}^+ $ concentration, not acid concentration directly). Option d is correct.
# Answer:
d. concentration of $ \text{H}^+_{(\text{aq})} $ ions

### Question 3
# Brief Explanations:
A weak acid is one that ionizes (dissociates) very slightly in water. Option a is too vague. Option b is incorrect (a dilute strong acid is still a strong acid, just less concentrated). Option c is incorrect (concentration and strength are different; a weak acid can be concentrated or dilute). Option d says "dissociates very slightly" and option e says "ionizes very slightly" – both are correct in meaning, but the standard definition refers to ionization (which includes dissociation for acids). However, among the options, e is a more precise definition as "ionizes" is the term used for acid behavior. Wait, no – actually, "dissociate" and "ionize" are often used interchangeably here. Wait, let's check: a weak acid ionizes (dissociates) only partially in water. So option d: "an acid that dissociates very slightly in a water solution" and option e: "an acid that ionizes very slightly in a water solution" – both are correct, but maybe the intended answer is e? Wait, no, maybe I made a mistake. Wait, the key is that weak acids have low ionization (dissociation) in water. So between d and e, "ionizes" is more accurate for acids (since acids donate protons, ionize to form $ \text{H}^+ $ and conjugate base). So option e is better? Wait, no, let's check the options again. Option d: "dissociates very slightly" – dissociation is the separation into ions, which is what happens. Option e: "ionizes very slightly" – ionization is the process of forming ions, which is the same as dissociation for acids. But maybe the answer is e? Wait, no, maybe the intended answer is d or e. Wait, actually, in chemistry, the term "ionize" is often used for acids (since they produce $ \text{H}^+ $ ions), so a weak acid ionizes slightly. So option e is correct. Wait, but let's check the options again: option d: "dissociates very slightly in a water solution" – dissociation is the breaking into ions, which is what acids do. Option e: "ionizes very slightly in a water solution" – ionization is the formation of ions, which is the same. But maybe the answer is e? Wait, no, maybe the answer is d? Wait, I think the standard definition is that a weak acid dissociates (ionizes) only partially in water. So both d and e are similar, but maybe the intended answer is e? Wait, no, let's see the options again. Option d: "dissociates very slightly" – dissociation is the process, and option e: "ionizes very slightly" – ionization is the process. But in the context of acids, ionization is the correct term (since acids are proton donors, and ionization involves the formation of $ \text{H}^+ $ ions). So option e is correct.
# Answer:
e. an acid that ionizes very slightly in a water solution

### Question 4
# Brief Explanations:
Nitric acid ($ \text{HNO}_3 $) is a strong acid, so it dissociates completely: $ \text{HNO}_3
ightarrow \text{H}^+ + \text{NO}_3^- $. So the concentration of $ \text{H}^+ $ is 1.4 mol/L. The pH is calculated as $ \text{pH} = -\log[\text{H}^+] $. So $ \text{pH} = -\log(1.4) \approx -0.15 $ (since $ \log(1.4) \approx 0.15 $, so negative of that is -0.15). Option a is just the concentration, not pH. Option b is way too high (pH can't be 14.15 for an acidic solution). Option c is -0.15, which is correct. Option d is 0.15 (positive, but log(1.4) is positive, so -log(1.4) is negative). Option e is incorrect.
# Explanation:
## Step 1: Determine $ [\text{H}^+] $
Since $ \text{HNO}_3 $ is a strong acid, it dissociates completely: $ \text{HNO}_3
ightarrow \text{H}^+ + \text{NO}_3^- $. So $ [\text{H}^+] = 1.4 \, \text{mol/L} $.
## Step 2: Calculate pH
Use the formula $ \text{pH} = -\log[\text{H}^+] $. Substitute $ [\text{H}^+] = 1.4 $:
$ \text{pH} = -\log(1.4) \approx -0.15 $ (because $ \log(1.4) \approx 0.15 $, so $ -\log(1.4) \approx -0.15 $).
# Answer:
c. $ -0.15 $

### Question 5
# Brief Explanations:
A saturated solution is defined as a solution that contains the maximum quantity of a solute that can dissolve at a specific temperature. Option a is correct. Option b (unsaturated) can dissolve more solute. Option c (supersaturated) contains more solute than the maximum, which is unstable. Option d (dissolved) is just a state, not a solution type. Option e is incorrect.
# Answer:
a. Saturated

### Question 6
# Brief Explanations:
Acids react with carbonates to produce $ \text{CO}_2 $, $ \text{H}_2\text{O} $, and a salt (e.g., $ 2\text{HCl} + \text{CaCO}_3
ightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \uparrow $). So option d ("They do not react with carbonates") is not a property of acids – it's incorrect, so it's the answer. Option a (taste sour) is a property of acids. Option b (pH < 7) is a property. Option c (react with metals) is a property (acids react with active metals to produce $ \text{H}_2 $). Option e (turn blue litmus red) is a property.
# Answer:
d. They do not react with carbonates.

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